Even Plants Eat Their Greens

By
Ashok Prasad
|
September 15, 2008 06:09am ET

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Bladderworts, carnivorous plants of the genus Utricularia,
live in water or soggy soil. To snare their snacks, bladderworts set
ingenious little traps, sometimes in the hundreds, among their
waterborne leaves. The traps maintain an internal pressure lower than
that outside; when passing prey triggers an exterior hair, a trapdoor
snaps open, and inflowing water carries the prey inside to be digested.

Biologists have long noted algae among the insects,
nematodes, and other minute animal prey in bladderwort traps. Are the
algae symbionts? Are they swept in accidentally with animals? Or could
bladderworts actually eat algae?

To advance the debate, Marianne Peroutka of the University of Vienna
and several colleagues analyzed 1,450 traps from four species of Utricularia.
More than half the traps contained algae, often unaccompanied by animal
prey. In fact, algae constituted as much as 80 percent of trap contents
under certain conditions.

Intriguingly, the softer the water the plant inhabited, the more algae its bladders bore.

Soft water, low in minerals, supports less animal life than hard
water does, and Peroutka thinks bladderworts may compensate for the
lack of meat by eating more greens. Indeed, some of the entrapped algae
appeared semi-digested, as others have noted.

A few other carnivorous plants are known to eat plant matter, so perhaps we should start calling them omnivores.